Cyanogen (C₂N₂) is a new type of fumigant that has the potential to replace methyl bromide. So it is of important significance to ascertain the behaviour of C₂N₂ in adsorption and transformation in soil for its safety application. Adsorption and transformation of C₂N₂ in soil was investigated using the static method under controlled conditions. C₂N₂ adsorption rates in soil was related with physicochemical properties of the soil, and slightly related with the ambient temperature, the soil water content and soil organisms, but not related with the application rate of the fumigant. C₂N₂ adsorption rate and its possible transformation products (HCN, NH₄⁺, NO₃^-and NO₂^-) were determined using the gas chromatography (GC) coupled with a nitrogen-phosphorus detector (NPD) and the flow injection analyzer (FIA) with a Photometric detector. Results show that the soil had a very high C₂N₂ adsorption capacity with a rate being over 75% within 2 h of fumigation and over 98% within 24 h. The absorbed C2N2 could be quickly transformed, about 13% into HCN, and 20% into NH₄⁺ and NO₃^-. No NO₂^-was detected within 48 h. HCN in soil was not stable and could be further transformed into other nitrogenous compounds.